Solid water-disintegrable composite and method for producing the same

Abstract

One or more aspects of the present invention provides a novel solid water-degradable complex which can readily degrade in room-temperature water despite including a polymer compound such as polyvinyl alcohol which is insoluble or slightly soluble in room-temperature water but soluble in hot water.　One or more aspects of the present invention relates to a solid water-degradable complex including a polymer compound which is insoluble or slightly soluble in water at 25°C but soluble in water at 80°C or more, and cellulose nanofibers having a sulfate ester group. One or more other aspects of the present invention is a method for manufacturing the complex, and relates to a method that includes: a step for preparing a dispersion containing a solvent and the cellulose nanofibers and the polymer compound dispersed in the solvent; and a step for obtaining the complex by removing the solvent from the dispersion.

Description

[Technical Field]

[0001] One or more aspects of the present invention relate to a solid water-disintegrable composite and a method for producing the same. [Background technology]

[0002] A water-disintegrating material is a material that is solid (for example, in the form of powder, fiber, film, etc.) in the absence of water and is easy to handle, but disintegrates and disperses in water when immersed in water.

[0003] An example of a water-disintegrating material is a water-soluble sheet-like color material disclosed in Patent Document 1, which comprises a film-forming water-soluble polymer, a dissolution promoter, a colorant, and a moisture-retaining agent. According to Patent Document 1, the water-soluble sheet-like color material has low adhesion, moderate self-supporting ability and flexibility, excellent handleability, and quickly becomes uniform when dissolved in water. Patent Document 1 lists polyvinyl alcohol, polyvinylpyrrolidone, water-soluble acrylic polymers, gelatin, starch, casein, polymeric polysaccharides, and the like as examples of film-forming water-soluble polymers.

[0004] Patent Document 1 describes that when polyvinyl alcohol is used as the film-forming water-soluble polymer, the degree of polymerization is preferably 1,500 to 5,000, and more preferably 2,000 to 4,500, and further describes that it is preferable to use polyvinyl alcohol with a degree of polymerization of 1,500 to 5,000 in combination with cellulose nanofibers as the film-forming water-soluble polymer.

[0005] Patent Document 1 further describes that the dissolution promoter is a component that has a relatively high water solubility and assists in the dissolution of a water-soluble film-forming polymer that has a relatively low water solubility, and that has the effect of promoting dissolution when the sheet-shaped color material is brought into contact with water, as well as having the effect of uniformly dispersing the colorant when the sheet-shaped color material is dissolved in water.Specific examples of the dissolution promoter include polyvinyl alcohol having a degree of polymerization of preferably 200 to 1,400, more preferably 300 to 1,000, and / or a fatty acid metal salt.

[0006] Meanwhile, growing environmental awareness has led to research around the world into the practical application of biomass-derived materials. For example, much of the cellulose extracted from wood (wood chips) is used in the form of paper, contributing significantly to both people's lives and CO2 fixation. Among cellulose, cellulose nanofibers in particular are used or desired for use in many fields. Cellulose nanofibers are biomass-derived compounds in which cellulose fibers are defibrated to nano-size. They disperse well in water, and transparent nanocellulose films can be easily obtained by drying the dispersion. Furthermore, when mixed with resins or rubbers, they can improve various physical properties, such as strength, flexibility, and elongation. They have attracted attention as a new, environmentally friendly material, and various proposals have been made.

[0007] For example, Patent Document 2 describes a method for producing fine cellulose fibers in which some of the hydroxyl groups of cellulose are oxidized to at least one functional group selected from the group consisting of carboxyl groups and aldehyde groups using an N-oxyl compound such as 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) as an oxidation catalyst.

[0008] Patent Document 3 describes a method for producing bionanofibers, which is a means for solving the problem of efficiently converting biomass such as cellulose, chitin, and chitosan into nanofibers and effectively utilizing biomass, and is characterized by spraying a biomass dispersion fluid at high pressure of 100 to 245 MPa and causing it to collide with a rigid collision body.

[0009] Patent Document 4 describes a method for producing cellulose nanofibers in which hydroxyl groups have been modified by sulfate esterification. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 2019-206646 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-1728 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-56456 [Patent Document 4] International Publication WO2018 / 131721 Summary of the Invention [Problem to be solved by the invention]

[0011] Among polyvinyl alcohols (PVA), high-molecular-weight PVA has excellent mechanical strength and moldability in the solid state, but is poorly soluble in water at room temperature and soluble in hot water. For this reason, Patent Document 1 discloses that when high-molecular-weight PVA is used as a water-disintegrable material in water at room temperature, it is combined with a low-molecular-weight PVA and a dissolution promoter such as a fatty acid metal salt. However, the present inventors discovered that a film made of high-molecular-weight PVA blended with low-molecular-weight PVA has inferior mechanical properties compared to a film made of high-molecular-weight PVA alone.

[0012] Therefore, one or more aspects of the present invention have an object to be achieved by providing a new solid water-disintegrable composite that contains a polymer compound, such as PVA, that is poorly soluble or insoluble in water at room temperature but soluble in hot water, yet can be easily disintegrated in water at room temperature. [Means for solving the problem]

[0013] The present inventors have found that materials containing water-soluble polymers such as carboxymethyl cellulose and xanthan gum instead of the low-molecular-weight PVA described in Patent Document 1, in order to improve the water-disintegration property of high-molecular-weight PVA at room temperature, also have inferior mechanical properties compared to materials consisting only of high-molecular-weight PVA.

[0014] Furthermore, the present inventors have found that a composite material of high molecular weight PVA and the TEMPO-oxidized cellulose nanofibers described in Patent Document 2 or the mechanically micronized cellulose nanofibers described in Patent Document 3 has superior mechanical strength compared to a material consisting of only high molecular weight PVA, but has poor water disintegration properties in water at room temperature.

[0015] As a result of intensive research, the inventors have found that a solid composite formed by combining cellulose nanofibers having sulfate ester groups with a polymer compound that is poorly soluble or insoluble in water at room temperature but soluble in hot water has superior mechanical properties and is more water-disintegratable in water at room temperature than a material consisting of the polymer compound alone, and have thus completed one or more aspects of the present invention described below.

[0016] (1) A polymer compound that is poorly soluble or insoluble in water at 25°C and soluble in water at 80°C or higher, and Cellulose nanofibers with sulfate ester groups A solid water-disintegrable composite comprising: (2) The complex according to (1), wherein the polymer compound is one or more selected from the group consisting of polyvinyl alcohol, starch, gelatin, carrageenan, agar, and derivatives thereof. (3) The composite according to (2), wherein the polymer compound is polyvinyl alcohol having a weight-average molecular weight of 60,000 g / mol or more and 220,000 g / mol or less. (4) The composite according to any one of (1) to (3), wherein the cellulose nanofibers are contained in an amount of 2% by mass or more and 98% by mass or less relative to the total amount of the polymer compound and the cellulose nanofibers. (5) The composite according to any one of (1) to (4), which is in the form of a film or fiber. (6) The complex according to any one of (1) to (5), which disintegrates in water at 25°C within 24 hours. (7) The composite according to any one of (1) to (6), wherein an aqueous dispersion prepared by dispersing the composite in water so that the concentration of the cellulose nanofibers is 0.3% by mass does not have spinnability at 25°C. (8) The composite according to any one of (1) to (7), wherein the viscosity of an aqueous dispersion prepared by dispersing the composite in water so that the concentration of the cellulose nanofibers is 0.3% by mass is 500 mPa·S or more, as measured at 25°C using a B-type viscometer at a rotor rotation speed of 2.6 rpm. (9) The composite according to any one of (1) to (8), wherein the thixotropy index (TI) value of an aqueous dispersion prepared by dispersing the composite in water so that the concentration of the cellulose nanofibers is 0.3% by mass is 3 to 30, the thixotropy index (TI) value being calculated from the viscosity measured at 25°C using a Brookfield viscometer at a rotor rotation speed of 2.6 rpm and the viscosity measured at 25°C using a Brookfield viscometer at a rotor rotation speed of 26 rpm.

[0017] (10) A method for producing the composite according to any one of (1) to (9), A step of preparing a dispersion containing a solvent, and the polymer compound and the cellulose nanofibers dispersed in the solvent; and removing the solvent from the dispersion to obtain the composite A method comprising: (11) The step of removing the solvent from the dispersion to obtain the composite includes: a step of removing the solvent from the dispersion layer to obtain the composite in the form of a film; The method according to (10), comprising: (12) The step of removing the solvent from the dispersion to obtain the composite includes: a step of mixing the dispersion liquid with a coagulation liquid to form a mixed liquid, and forming a coagulated material containing the polymer compound and the cellulose nanofibers in the mixed liquid; and removing the solvent from the layer of the coagulated material to obtain the composite in the form of a film; The method according to (10), comprising: (13) The step of removing the solvent from the dispersion to obtain the composite includes: A step of discharging the dispersion liquid from a nozzle to form a fibrous discharged product; and a step of removing the solvent from the discharged product to obtain the fibrous composite material The method according to (10), comprising: This specification includes the disclosure of Japanese Patent Application No. 2022-017930, from which the present application claims priority. [Effects of the Invention]

[0018] According to one or more aspects of the present invention, there is provided a novel solid water-disintegrable composite that contains a polymer compound, such as PVA, that is poorly soluble or insoluble in water at room temperature but soluble in hot water, yet can be easily disintegrated in water at room temperature. DETAILED DESCRIPTION OF THE INVENTION

[0019] 1. Polymer compounds The polymer compounds that are poorly soluble or insoluble in water at 25° C. and soluble in water at 80° C. or higher, which are used in one or more embodiments of the present invention, are described below.

[0020] "Slightly soluble or insoluble in water at 25°C" specifically means that the solubility in water at 25°C is 0 g / 100 g or more and 1 g / 100 g or less, preferably 0 g / 100 g or more and 0.1 g / 100 g or less.

[0021] "Soluble in water at 80°C or higher" specifically means that the solubility in water at 80°C or higher is 10 g / 100 g or higher, preferably 30 g / 100 g or higher. A polymer compound that exhibits a solubility in the above range when thoroughly stirred in water at 80°C or higher for 30 minutes or more can be said to be "soluble in water at 80°C or higher."

[0022] Such polymer compounds, which exhibit solubility characteristics of being poorly soluble or insoluble in water at room temperature (20°C to 30°C; the same applies below) and soluble in hot water (water at 80°C or higher; the same applies below), are not suitable for use alone as water-disintegrating materials in water at room temperature. However, the present inventors have made the unexpected discovery that a solid composite containing the polymer compound and cellulose nanofibers having sulfate ester groups, as described below, can be easily disintegrated in water at room temperature and can be used as a water-disintegrating material.

[0023] The polymer compound exhibiting the above-mentioned solubility characteristics is preferably one or more selected from the group consisting of polyvinyl alcohol, starch, gelatin, carrageenan, agar, and derivatives thereof, and is particularly preferably polyvinyl alcohol (PVA).The PVA exhibiting the above-mentioned solubility characteristics is preferably a high-molecular-weight PVA.

[0024] The high-molecular-weight PVA preferably has a weight-average molecular weight of 60,000 g / mol or more and 220,000 g / mol or less, more preferably 64,000 g / mol or more, more preferably 200,000 g / mol or less, more preferably 150,000 g / mol or less, and more preferably 100,000 g / mol or less. Such high-molecular-weight PVA is preferred because it has excellent moldability in the solid state and high mechanical properties such as elastic modulus and strength.

[0025] The weight average molecular weight of PVA can be measured by gel permeation chromatography (GPC) using PVA or polystyrene as a standard substance.

[0026] 2. Cellulose nanofibers with sulfate ester groups Next, we will explain the cellulose nanofibers having sulfate ester groups used in one or more embodiments of the present invention. The cellulose nanofibers will also be referred to as "sulfate-esterified cellulose nanofibers" or "sulfate-esterified CNFs."

[0027] Ordinary cellulose (unmodified cellulose) is a polysaccharide in which glucose is linked via β-1,4-glycosidic bonds (C6H 10 O5) n The cellulose nanofibers used in this embodiment are fibers made of modified cellulose having sulfate ester groups.

[0028] The solid composite according to this embodiment, which contains the sulfated CNF and the polymer compound, has better water-disintegratability than a solid composite in which cellulose nanofibers that do not contain sulfate ester groups are combined with the polymer compound instead of the sulfated CNF that has sulfate ester groups.

[0029] Furthermore, the solid composite according to this embodiment, which contains the sulfated CNF and the polymer compound, has superior mechanical properties compared to a material consisting of only the polymer compound or a solid composite in which a water-soluble polymer such as carboxymethyl cellulose or xanthan gum is blended in place of the sulfated CNF.

[0030] The average fiber width of the sulfated CNF is not particularly limited, but is, for example, 1 nm to 1000 nm, preferably 1 nm to 100 nm, and more preferably 2 nm to 10 nm.The average fiber length of the sulfated CNF is not particularly limited, but is usually 0.1 μm to 6 μm, and preferably 0.1 μm to 2 μm.

[0031] The average fiber width and average fiber length of the sulfated CNF can be measured by, for example, using an atomic force microscope (SPM-9700HT, manufactured by Shimadzu Corporation) to measure the fiber width (fiber diameter (equivalent circle diameter)) and fiber length of 50 arbitrarily selected fibers and calculating the arithmetic mean. The average fiber width and average fiber length can be set within the desired range by adjusting the concentration of reagents such as sulfuric acid during the production of the sulfated CNF, the amount of pulp relative to the reaction solution, and the reaction time.

[0032] The sulfated CNF has sulfate ester groups represented by the following general formula (1): The sulfated CNF is usually produced by substituting some of the OH groups in the cellulose that constitutes the fiber with sulfate ester groups represented by general formula (1). The sulfated CNF can be produced, for example, by sulfate esterifying and defibrating raw pulp, as shown in the examples.

[0033] [ka] (In the general formula (1), n ​​is an integer of 1 to 3, and M n+ is an n-valent cation, and the wavy lines are the bonding sites to other atoms.)

[0034] M n+ As for hydrogen ions (H + ), metal ions, ammonium ions, etc. When n is 2 or 3, M n+ is two or three -OSO3 - It forms an ionic bond with

[0035] Examples of metal ions include alkali metal ions, alkaline earth metal ions, transition metal ions, and other metal ions.

[0036] Here, the alkali metal ions include lithium ions (Li + ), sodium ions (Na + ), potassium ions (K +), rubidium ion (Rb + ), cesium ions (Cs + ) and the like. Examples of alkaline earth metal ions include calcium ions (Ca 2+ ), strontium ions (Sr 2+ ) and the like. Examples of transition metal ions include iron ions, nickel ions, palladium ions, copper ions, and silver ions. Examples of other metal ions include beryllium ions, magnesium ions, zinc ions, and aluminum ions.

[0037] The ammonium ion is NH4 + Not only NH4 + Ammonium ions derived from various amines in which one or more hydrogen atoms are replaced by organic groups are also included. Ammonium ions include, for example, NH4 + , quaternary ammonium cation, alkanolamine ion, pyridinium ion, etc.

[0038] M n+ As the cation, hydrogen ion, sodium ion, potassium ion, calcium ion, or quaternary ammonium cation is preferred, and sodium ion (Na + It is particularly preferable that M of the sulfate ester group represented by the general formula (1) is n+ The number of types may be one or more.

[0039] When the sulfated CNF has sulfate ester groups introduced by substituting some of the OH groups in the cellulose that constitutes the fiber with sulfate ester groups represented by general formula (1), the wavy line indicates the bonding site to the carbon atom to which the OH group was bonded.

[0040] The sulfated CNF may have other substituents in addition to the sulfate ester group represented by the general formula (1). When the sulfated CNF has a group other than the sulfate ester group represented by the general formula (1), i.e., other substituents, the other substituents typically substitute for at least one of the OH groups in the cellulose constituting the cellulose nanofibers. Examples of other substituents include, but are not limited to, anionic substituents and their salts, ester groups, ether groups, acyl groups, aldehyde groups, alkyl groups, alkylene groups, aryl groups, and combinations of two or more of these. When two or more other substituents are used in combination, the content ratio of each substituent is not limited. Among the other substituents, anionic substituents and their salts, or acyl groups are preferred from the viewpoint of nano-dispersibility. As anionic substituents and their salts, carboxyl groups, phosphate ester groups, phosphite ester groups, and xanthate groups are particularly preferred. When the anionic substituent is in the form of a salt, sodium salts, potassium salts, and calcium salts are particularly preferred from the viewpoint of nano-dispersibility. Furthermore, an acetyl group is a particularly preferred acyl group from the viewpoint of nano-dispersibility.

[0041] The amount of sulfur introduced into the sulfated CNF due to sulfate ester groups can be, for example, 0.3 mmol / g or more and 3.0 mmol / g or less. The amount of sulfate ester groups introduced can be set to any appropriate value within the above range depending on the application, etc. The amount of sulfur introduced into the sulfated CNF due to sulfate ester groups can be expressed as the sulfur content (mmol) per 1 g of cellulose nanofiber. The amount of sulfur introduced is preferably 0.4 mmol / g or more and 2.5 mmol / g or less, and more preferably 0.8 mmol / g or more and 2.0 mmol / g or less. A sulfur introduction amount within the above range is preferred from the viewpoint of high water dispersibility after drying.

[0042] The amount of sulfur introduced can be determined, for example, by the combustion absorption-ion chromatography (IC) method (combustion absorption-IC method, combustion IC method) described in the Examples. The amount of sulfur introduced can be adjusted, for example, by controlling the concentration of a reagent such as sulfuric acid in the solution (defibration solution) used to defibrate the pulp, the amount of pulp relative to the defibration solution, the reaction time, the reaction temperature, etc.

[0043] 3. Water-disintegrating composite One or more aspects of the present invention include: A polymer compound that is poorly soluble or insoluble in water at 25°C and soluble in water at 80°C or higher, and Cellulose nanofibers with sulfate ester groups A solid water-disintegrable composite comprising Regarding.

[0044] The water-disintegratable composite according to this embodiment has water-disintegratability and can therefore be used as easily dismantled or biodegradable molded articles (packaging, etc.), easily dismantled adhesives, coating agents, paints, cosmetics, etc.

[0045] In the water-disintegrable composite according to this embodiment, the blending ratio of the polymer compound to the sulfated CNF is not particularly limited. The higher the proportion of the sulfated CNF relative to the polymer compound, the higher the water-disintegrability of the composite. The lower the proportion of the sulfated CNF, the higher the strength and elastic modulus of the composite. Therefore, the blending ratio can be appropriately adjusted depending on the desired mechanical properties and water-disintegrability. In the water-disintegrable composite according to this embodiment, the content of the sulfated CNF relative to the total amount of the polymer compound and the sulfated CNF can be, for example, 2% by mass or more and 98% by mass or less, preferably 5% by mass or more and 95% by mass or less, more preferably 8% by mass or more and 92% by mass or less, and particularly preferably 10% by mass or more and 90% by mass or less.

[0046] The water-disintegrable composite according to this embodiment may contain, in addition to the polymer compound and the sulfated CNF, one or more other components depending on the intended use. The other components may be water, an inorganic component, and / or an organic component.

[0047] Examples of inorganic components include inorganic fine particles, such as silica, mica, talc, clay, carbon, carbonates (e.g., calcium carbonate, magnesium carbonate), oxides (e.g., aluminum oxide, titanium oxide, zinc oxide, iron oxide), ceramics (e.g., ferrite), and mixtures thereof.

[0048] The organic component may be, for example, at least one substance selected from the group consisting of resins and rubbers. Examples of resins and rubbers include phenolic resins, melamine resins, urea resins, alkyd resins, epoxy resins, unsaturated polyester resins, polyurethane resins, polyethylene resins (e.g., high-density polyethylene, medium-density polyethylene, and low-density polyethylene), polypropylene resins, polystyrene resins, acrylic resins, polyvinyl alcohol, acrylamide resins, silicone resins, natural rubber, and synthetic rubber. The organic compound may also be a functional compound. Examples of functional compounds include dyes, UV absorbers, antioxidants, antistatic agents, and surfactants.

[0049] The water-disintegrable composite according to this embodiment may contain the polymer compound and the sulfated CNF in a total amount of 60% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, more preferably 95% by mass or more, and more preferably 98% by mass or more, with at least a portion of the remainder containing one or more of the other components listed above. The water-disintegrable composite according to this embodiment may contain the polymer compound and the sulfated CNF in a total amount of 100% by mass.

[0050] The shape of the water-disintegratable composite according to this embodiment is not particularly limited as long as it is solid, but it can be in the form of a film, fiber, powder, granules, etc., and a film or fiber shape is particularly preferred. The thickness of the film, the planar dimensions and planar shape of the film, and the thickness and length of the fiber are not particularly limited and can be set appropriately depending on the purpose. The water-disintegratable composite according to this embodiment in the form of a film or fiber may be further molded into a desired three-dimensional shape.

[0051] The water-disintegrable composite according to this embodiment preferably disintegrates in water at 25°C within 24 hours. The amount of water at 25°C is not particularly limited as long as it is an excess amount relative to the water-disintegrable composite according to this embodiment, but for example, an amount of water that results in a concentration of the sulfated CNF in the water-disintegrable composite according to this embodiment of 0.3% by mass or less can be used. "Disintegrating in water at 25°C within 24 hours" means that when a sample of the water-disintegrable composite according to this embodiment is immersed in water at 25°C and allowed to stand, the time required for the sample to partially separate and become unable to be grasped with tweezers is within 24 hours.

[0052] In a more preferred embodiment of the water-disintegrable composite according to this aspect, an aqueous dispersion prepared by dispersing the composite in water so that the cellulose nanofiber concentration is 0.3% by mass does not exhibit spinnability at 25°C. The water-disintegrable composite according to this embodiment is easy to handle, in that it does not leave sticky hands when touched and the dispersion obtained by disintegration in water does not easily adhere to containers. The inventors have found that aqueous dispersions of water-disintegrable composites prepared by blending a water-soluble polymer such as low-molecular-weight PVA, carboxymethyl cellulose, or xanthan gum with the polymer compound, rather than the sulfated CNF, exhibit spinnability at 25°C but are difficult to handle, whereas aqueous dispersions of water-disintegrable composites prepared by blending the sulfated CNF with the polymer compound can be made non-spinnable at 25°C. Spinnability can be evaluated by the method described in the Examples.

[0053] In a more preferred embodiment of the water-disintegrable composite according to this aspect, the composite is dispersed in water to a concentration of the sulfated CNF of 0.3% by mass, and the viscosity of the aqueous dispersion prepared by measuring at 25°C using a Brookfield viscometer with a rotor rotation speed of 2.6 rpm is 500 mPa·S or more, more preferably 2000 mPa·S or more, more preferably 4000 mPa·S or more, even more preferably 5000 mPa·S or more, and more preferably 10000 mPa·S or less, more preferably 8000 mPa·S or less, and even more preferably 7000 mPa·S or less. This viscosity is imparted by the viscosity of the sulfated CNF, and therefore no additional thickener is required for the water-disintegrable composite according to this embodiment.

[0054] In a more preferred embodiment of the water-disintegrable composite according to this aspect, the composite is dispersed in water to a concentration of 0.3% by mass of the sulfated CNF to prepare an aqueous dispersion. The thixotropy index (TI) value, calculated from the viscosity measured at 25°C using a Brookfield viscometer at a rotor rotation speed of 2.6 rpm and the viscosity measured at 25°C using a Brookfield viscometer at a rotor rotation speed of 26 rpm, is preferably 3 to 30, more preferably 4 to 20, and even more preferably 5 to 15. This thixotropy is imparted by the sulfated CNF, and the water-disintegrable composite according to this embodiment does not require the addition of a separate thixotropic agent. The TI value can be calculated using the following formula: TI value = (viscosity measured at 2.6 rpm) / (viscosity measured at 26 rpm)

[0055] 4. Manufacturing method of water-disintegrable composite Another aspect of the present invention is to provide a method for manufacturing a semiconductor device comprising: A method for producing a water-disintegratable composite according to one or more of the above aspects, A step of preparing a dispersion containing a solvent, and the polymer compound and the cellulose nanofibers dispersed in the solvent; and removing the solvent from the dispersion to obtain the composite A method including Regarding.

[0056] The method according to this embodiment makes it possible to produce the water-disintegrable composite according to one or more of the above-described embodiments.

[0057] The dispersion contains a solvent, the polymer compound, and the cellulose nanofibers dispersed in the solvent, and may further contain one or more of the other components described above, as necessary. Here, "dispersion" refers to "dissolution" and / or "suspension."

[0058] As the solvent, a solvent that can dissolve the polymer compound and disperse the cellulose nanofibers can be suitably used, and specific examples include water and dimethyl sulfoxide (DMSO). In the step of preparing the dispersion, stirring is carried out as necessary to uniformly disperse each component in water.

[0059] The amount of the solvent is not particularly limited as long as it is an amount that can dissolve the soluble components in the solvent and uniformly suspend the insoluble components, but for example, it can be an amount that makes the concentration of the sulfated CNF in the dispersion 0.3 mass% or less.

[0060] The order in which the components are added to the solvent to prepare the dispersion is not particularly limited.

[0061] When water is used as the solvent, in the step of preparing the dispersion, it is preferable to disperse the polymer compound in water at a temperature of 80°C or higher. The temperature of the water is preferably a temperature at which the polymer compound can be dissolved, more preferably 90°C or higher, and more preferably 100°C or lower. After dispersing the polymer compound in water at 80°C or higher, the temperature of the water may be lowered to a temperature below 80°C, for example, to room temperature. There are no particular restrictions on the timing of adding the cellulose nanofibers and, optionally, the one or more other components to the dispersion. In a preferred embodiment of the step of preparing the dispersion, the cellulose nanofibers and the polymer compound are added to and dispersed in water at 80°C or higher to prepare the dispersion. In another preferred embodiment of the step of preparing the dispersion, after dispersing the polymer compound in water at 80°C or higher to obtain a polymer compound dispersion, the temperature of the polymer compound dispersion is lowered to a temperature below 80°C, and then the cellulose nanofibers are dispersed in the polymer compound dispersion to prepare the dispersion.

[0062] When a solvent such as DMSO that can disperse each component sufficiently at room temperature is used as the solvent, the order in which each component is added to the solvent can be set more freely.

[0063] In the method according to this embodiment, the step of removing the solvent from the dispersion to obtain the composite (drying step) is a step of removing the solvent from the dispersion by a drying process such as air drying, freeze drying, hot air drying, vacuum drying, or spray drying. The drying step can be appropriately selected depending on the desired shape of the water-disintegrable composite. For example, the dispersion can be spray-dried to obtain a powdery water-disintegrable composite.

[0064] In a preferred embodiment of the method according to this aspect, in order to produce a film-like water-disintegrable composite, the drying step comprises: a step of removing the solvent from the dispersion layer to obtain the composite in the form of a film; Includes. In this embodiment, the layer of the dispersion can be formed by spreading the dispersion on the bottom of an appropriate container, and the thickness of the layer can be appropriately set taking into consideration the concentrations of the components in the dispersion, the desired thickness of the film-like water-disintegrable composite, etc. The solvent can be removed from the layer by a drying process such as air drying, freeze drying, hot air drying, or vacuum drying.

[0065] In another preferred embodiment of the method according to the present aspect, in order to produce a film-like water-disintegrable composite, the drying step comprises: a step of mixing the dispersion liquid with a coagulation liquid to form a mixed liquid, and forming a coagulated material containing the polymer compound and the cellulose nanofibers in the mixed liquid; and removing the solvent from the layer of the coagulated material to obtain the composite in the form of a film; Includes.

[0066] The coagulation liquid is not particularly limited as long as it can precipitate a coagulated product containing the polymer compound and the cellulose nanofibers in a mixed liquid when mixed with the dispersion, but examples of coagulation liquids include acetone, alcohol (methanol, ethanol, isopropyl alcohol, etc.), aqueous sodium sulfate (Na2SO4), aqueous ammonium sulfate ((NH4)2SO4), aqueous zinc sulfate (ZnSO4), aqueous magnesium sulfate (MgSO4), and aqueous aluminum sulfate (Al2(SO4)3). The coagulation agents described in this paragraph can also be used in the wet spinning method described below.

[0067] The coagulum layer can be obtained by forming the coagulum at the bottom of a suitable container. The thickness of the layer can be appropriately set taking into consideration the concentrations of the components in the dispersion, the desired thickness of the film-like water-disintegrable composite, etc. The solvent can be removed from the layer by a drying process such as air drying, freeze drying, hot air drying, or vacuum drying.

[0068] In yet another preferred embodiment of the method according to the present aspect, in order to produce a fibrous water-disintegrable composite, the drying step a step of discharging the dispersion liquid from a nozzle to form a fibrous discharged material (fiber formation step); and A step of removing the solvent from the discharged product to obtain the fibrous composite (fiber drying step). Includes.

[0069] The fiberization step and the fiber drying step may be carried out simultaneously or sequentially.

[0070] An example of a method for simultaneously performing the fiber forming step and the fiber drying step is a dry spinning method, in which the dispersion is discharged from a nozzle into an atmosphere at a temperature at which the solvent volatilizes to form a fibrous discharged product, and the solvent is volatilized and removed from the discharged product to obtain the fibrous composite.

[0071] An example of a method in which the fiberization step and the fiber drying step are carried out in sequence is a wet spinning method. In the wet spinning method, the fiberization step involves discharging the dispersion from a nozzle into a coagulation liquid, and forming a fibrous extrusion (coagulation) containing the polymer compound and the cellulose nanofibers in the coagulation liquid. The coagulation liquid described in relation to the other preferred embodiment above can be used as the coagulation liquid. The wet spinning method also includes a fiber drying step in which the solvent is removed from the fibrous extrusion obtained in the fiberization step. The solvent can be removed from the fibrous extrusion by a drying process such as air drying, freeze drying, hot air drying, or vacuum drying. [Example]

[0072] <Method for producing sulfated CNF (cellulose nanofiber)> 150 g of dimethyl sulfoxide (DMSO), 25 g of acetic anhydride (concentration in defibration solution: 14% by mass), and 3.35 g of sulfuric acid (concentration in defibration solution: 1.87% by mass) were placed in a 300 ml sample bottle and stirred for approximately 30 seconds using a magnetic stirrer at room temperature of 25°C to prepare a defibration solution.

[0073] Next, 5.0 g of softwood kraft pulp NBKP (manufactured by Nippon Paper Industries Co., Ltd.) was added to the defibrating solution and stirred for an additional 30 minutes (2 hours) at room temperature of 25°C to carry out a sulfate esterification reaction. After stirring, 250 ml of distilled water was added to the cellulose-containing defibrating solution to stop the reaction, and then a 5% by mass aqueous solution of sodium hydroxide was added until the pH reached 7 to neutralize the reaction solution. The supernatant was then removed by centrifugation.

[0074] An additional 1350 ml of distilled water was added and stirred until uniformly dispersed, after which the supernatant was removed by centrifugation. The same procedure was repeated three times for washing. After washing by centrifugation, distilled water was added and the total weight was diluted to 500 g.

[0075] Next, the mixture was stirred for 3 minutes using a mixer (G5200, manufactured by Biolomix) to obtain a uniform aqueous dispersion of cellulose nanofibers with sulfate ester groups (sulfate-esterified CNF) with a concentration of 1% by mass.

[0076] <Quantitative determination of the amount of sulfate ester groups introduced> The sulfur content due to sulfated CNF was quantified using the combustion absorption-IC method. Specifically, dried sulfated CNF (0.01 g) was placed on a magnetic board and burned in a circular furnace (1350 °C) under an oxygen atmosphere (flow rate: 1.5 L / min). The generated gas components were absorbed in 3% hydrogen peroxide (20 ml). The resulting absorbed solution was diluted to 100 ml with pure water, and the sulfate ion concentration (mass%) of the diluted solution was measured by ion chromatography. Based on the measurement results, the amount of sulfur introduced (mmol / g) due to sulfate ester groups per 1 g of sulfated CNF was calculated.

[0077] The amount of sulfate ester groups introduced into the sulfated CNF prepared above, measured by this method, was 1.7 mmol / g.

[0078] <Polyvinyl alcohol (PVA)> The PVA used was a PVA manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., with a molecular weight of approximately 65,000.

[0079] <Preparation of Composite Material of PVA and Sulfuric Acid Esterified CNF (Cellulose Nanofiber)> PVA:Sulfuric Acid Esterified CNF = 9:1 4.05 g of PVA and 850.95 g of water were added to 45 g of 1% sulfuric acid esterified CNF aqueous dispersion. Then, it was heated to 80°C and stirred to dissolve PVA, obtaining an aqueous mixed solution of PVA and sulfuric acid esterified CNF.

[0080] PVA:Sulfuric Acid Esterified CNF = 5:5 0.45 g of PVA and 134.55 g of water were added to 45 g of 1% sulfuric acid esterified CNF aqueous dispersion. Then, it was heated to 80°C and stirred to dissolve PVA, obtaining an aqueous mixed solution of PVA and sulfuric acid esterified CNF.

[0081] PVA:Sulfuric Acid Esterified CNF = 1:9 0.05 g of PVA and 54.95 g of water were added to 45 g of 1% sulfuric acid esterified CNF aqueous dispersion. Then, it was heated to 80°C and stirred to dissolve PVA, obtaining an aqueous mixed solution of PVA and sulfuric acid esterified CNF.

[0082] 100 g of the above aqueous mixed solution was put into a 10×20 cm plastic container and dried at 50°C for 10 hours using a forced-air dryer, and then dried at 105°C for 1 hour using the forced-air dryer to prepare a film-like composite of sulfuric acid esterified CNF and PVA with a thickness of 20 μm.

[0083] The above aqueous mixed solution was slowly discharged from the nozzle of a syringe filled with 100 g of the aqueous mixed solution into 500 ml of acetone (coagulating liquid) to obtain a fibrous discharge of the mixture of sulfuric acid esterified CNF and PVA. The discharge was taken out of acetone and dried at 50°C for 10 hours using a forced-air dryer, and then dried at 105°C for 1 hour using the forced-air dryer to prepare a fibrous composite of sulfuric acid esterified CNF and PVA.

[0084] <Preparation of Comparative Sample> (PVA (100%)) 99.5 g of water was added to 0.5 g of PVA, and the mixture was then heated to 80°C and stirred to dissolve the PVA in water, yielding an aqueous solution of PVA.

[0085] 100 g of the aqueous solution was placed in a 10 x 20 cm plastic container and dried using a blower dryer at 50°C for 10 hours, and then dried using a blower dryer at 105°C for 1 hour to produce a 20 μm thick film of PVA.

[0086] The aqueous solution (100 g) was slowly dispensed into 500 ml of acetone (coagulation liquid) from the nozzle of a syringe, and the dispensed product was removed from the acetone and dried at 50°C for 10 hours using a blower dryer, followed by another drying at 105°C for 1 hour to produce fibrous PVA.

[0087] (PVA (90%) low molecular weight PVA (10%)) 4.05 g of PVA and 0.45 g of low-molecular-weight PVA (molecular weight approximately 20,000) were added to 895.5 g of water. The mixture was then heated to 80°C and stirred to dissolve the PVA and low-molecular-weight PVA in water, yielding a mixed aqueous solution of PVA and low-molecular-weight PVA.

[0088] 100 g of the aqueous solution was placed in a 10 x 20 cm plastic container and dried using a blower dryer at 50°C for 10 hours, and then dried using a blower dryer at 105°C for 1 hour to produce a 20 μm thick film-like composite of PVA and low-molecular-weight PVA.

[0089] The mixed aqueous solution was slowly dispensed into 500 ml of acetone (coagulation liquid) from the nozzle of a syringe loaded with 100 g of PVA solution, yielding a fibrous PVA extruded product. The extruded product was removed from the acetone and dried at 50°C for 10 hours using a blower dryer, and then at 105°C for 1 hour using a blower dryer to produce fibrous PVA.

[0090] (PVA (90%) CMC (10%)) 4.05 g of PVA and 0.45 g of CMC were added to 895.5 g of water. The mixture was then heated to 80°C and stirred to dissolve the PVA and CMC in water, yielding a mixed aqueous solution of PVA and CMC.

[0091] 100 g of the aqueous solution was placed in a 10 x 20 cm plastic container and dried at 50°C for 10 hours using a blower dryer, and then dried at 105°C for 1 hour using a blower dryer to produce a 20 μm thick film of PVA and CMC composite.

[0092] (PVA (90%), xanthan gum (10%)) 4.05 g of PVA and 0.45 g of xanthan gum were added to 895.5 g of water. The mixture was then heated to 80°C and stirred to solubilize the PVA and xanthan gum, yielding an aqueous solution of the PVA and xanthan gum mixture.

[0093] 100 g of the aqueous solution was placed in a 10 x 20 cm plastic container and dried using a blower dryer at 50°C for 10 hours, and then dried using a blower dryer at 105°C for 1 hour to produce a 20 μm thick film of PVA and xanthan gum composite.

[0094] (PVA (90%), mechanically processed CNF (10%)) The mechanically processed CNFs used were BiNFi-s and WFo-10002 manufactured by Sugino Machine Co., Ltd.

[0095] 4.05g of PVA and 850.95g of water were added to 45g of 1% aqueous dispersion of mechanically treated CNF. The mixture was then heated to 80°C and stirred to dissolve the PVA, yielding an aqueous mixture of PVA and mechanically treated CNF.

[0096] 100 g of the aqueous solution was placed in a 10 x 20 cm plastic container and dried using a blower dryer at 50°C for 10 hours, and then dried using a blower dryer at 105°C for 1 hour to produce a 20 μm thick film-like composite of PVA and mechanically treated CNF.

[0097] (PVA (90%) TEMPO-oxidized CNF (10%))

[0098] 0.13 mmol of 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) and 10 mmol of sodium bromide were dissolved in water to obtain a 250 mL aqueous solution. 5 g of absolute dry softwood kraft pulp (NBKP, manufactured by Nippon Paper Industries Co., Ltd.) was added to this solution and stirred until the pulp was uniformly dispersed. After the mixture was brought to 20°C, 32 mmol of aqueous sodium hypochlorite solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to initiate the oxidation reaction. During the reaction, the temperature of the reaction system was maintained at 20°C, and the pH was maintained at 10 by gradually adding 3N aqueous sodium hydroxide solution. After 3 hours of reaction, the resulting product was filtered through a glass filter, the filter cake was thoroughly washed with water, and water was added to bring the total weight to 500 g. Next, the mixture was stirred for 3 minutes using a mixer (G5200, manufactured by Biolomix) to obtain a uniform aqueous dispersion of TEMPO-oxidized CNF with a concentration of 1% by mass.

[0099] 4.05g of PVA and 850.95g of water were added to 45g of 1% TEMPO-oxidized CNF aqueous dispersion. The mixture was then heated to 80°C and stirred to dissolve the PVA, yielding a mixed aqueous solution of PVA and TEMPO-oxidized CNF.

[0100] <Evaluation test 1 (Table 2)> The composite film of PVA (90%) and sulfated CNF (10%) prepared above and a comparative film were evaluated for their water disintegration, spinnability, viscosity characteristics, and reinforcing properties. The results are shown in Table 2.

[0101] Water disintegration was evaluated using the following procedure. 0.1 g of a sample was added to 100 g of water at 25°C in a beaker and allowed to stand. After a predetermined time had passed, the sample was judged to have disintegrated when grasped with tweezers (whether a portion separated and could not be grasped with tweezers). The time at which the sample first disintegrated was defined as the "water disintegration time." Samples whose water disintegration time was within 1 hour were rated "A1," samples whose water disintegration time was between 1 and 2 hours were rated "A2," samples whose water disintegration time was between 2 and 24 hours were rated "A3," and samples that did not disintegrate within 24 hours were rated "Y."

[0102] Spinnability was evaluated using the following procedure. 0.1 g of sample was added to 100 g of water at 25°C in a beaker and stirred for 6 hours using a magnetic stirrer. After stirring, the tip of a glass rod was immersed in the dispersion and then removed. If threads were formed, the sample was evaluated as having spinnability (yes); if no threads were formed, the sample was evaluated as having spinnability (no).

[0103] The viscosity characteristics were evaluated using the following procedure. A sample with the weight shown in Table 1 below was added to 100 g of water at 25°C in a beaker and stirred for 6 hours using a magnetic stirrer. After stirring, 100 g of the resulting uniform dispersion was degassed for 10 seconds using a degassing device (Thinky ARE-310) and allowed to stand at 25°C for 24 hours. The viscosity of the dispersion after standing was measured at 25°C using a Brookfield DV-II+ viscometer with a rotor rotation speed of 2.6 rpm and 26 rpm. A No. 62 rotor was used for the measurements. The viscosity was recorded 10 minutes after the start of viscosity measurement three times, and the average value was used as the viscosity of the dispersion. The TI (thixotropy index) value was calculated by multiplying the viscosity measured at 2.6 rpm by the viscosity measured at 26 rpm (JIS K 6833-1:2008).

[0104] [Table 1]

[0105] The reinforcement was evaluated using the following procedure. The elastic modulus and strength of each sample were determined by a tensile test (based on JIS K 7176-1 for films in evaluation tests 1 and 2, and JIS R 7606:2000 for fibers in evaluation test 2). The reinforcement of samples whose elastic modulus and strength exceeded those of samples of the same shape made of 100% PVA was evaluated as "Good," and the reinforcement of other samples was evaluated as "Poor."

[0106] [Table 2]

[0107] <Evaluation test 2 (Table 4)> The water disintegration, spinnability, viscosity properties, and reinforcing properties of film-like and fibrous samples of the composites of PVA and sulfated CNF prepared above at different mass ratios were evaluated. The evaluation methods were as described in "Evaluation Test 1 (Table 2)." The weights of the samples used to measure viscosity properties are shown in Table 3. The results are shown in Table 4.

[0108] [Table 3]

[0109] [Table 4] All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety.

Claims

1. A polymer compound that is poorly soluble or insoluble in water at 25°C and soluble in water at 80°C or higher, and Cellulose nanofibers with sulfate ester groups Contains the polymer compound is polyvinyl alcohol having a weight average molecular weight of 60,000 g / mol or more and 150,000 g / mol or less; Solid, water-disintegrating composite.

2. 2. The composite according to claim 1, wherein the polymer compound is polyvinyl alcohol having a weight average molecular weight of 60,000 g / mol or more and 100,000 g / mol or less.

3. The composite according to claim 1, wherein the cellulose nanofibers are contained in an amount of 2% by mass or more and 98% by mass or less relative to the total amount of the polymer compound and the cellulose nanofibers.

4. The composite described in claim 2, containing 10% by mass or more and 90% by mass or less of the cellulose nanofiber relative to the total amount of the polymer compound and the cellulose nanofiber.

5. The composite of claim 1 in the form of a film or fiber.

6. The complex according to claim 1, which loses its shape in water at 25°C within 24 hours.

7. 2. The composite according to claim 1, wherein an aqueous dispersion prepared by dispersing the composite in water so that the concentration of the cellulose nanofibers is 0.3% by mass does not have spinnability at 25°C.

8. The composite according to claim 1, wherein the viscosity of an aqueous dispersion prepared by dispersing the composite in water so that the concentration of the cellulose nanofibers is 0.3% by mass is 500 mPa·S or more, as measured at 25°C using a Brookfield viscometer at a rotor rotation speed of 2.6 rpm.

9. The composite according to claim 1, wherein the thixotropy index (TI) value of an aqueous dispersion prepared by dispersing the composite in water so that the concentration of the cellulose nanofiber is 0.3% by mass is 3 to 30, the thixotropy index (TI) value being calculated from the viscosity measured at 25°C using a Brookfield viscometer at a rotor rotation speed of 2.6 rpm and the viscosity measured at 25°C using a Brookfield viscometer at a rotor rotation speed of 26 rpm.

10. A method for producing the composite according to any one of claims 1 to 9, A step of preparing a dispersion containing a solvent, and the polymer compound and the cellulose nanofibers dispersed in the solvent; and removing the solvent from the dispersion to obtain the composite A method comprising:

11. a step of removing the solvent from the dispersion to obtain the composite, a step of removing the solvent from the dispersion layer to obtain the composite in the form of a film; The method of claim 10, comprising:

12. a step of removing the solvent from the dispersion to obtain the composite, a step of mixing the dispersion liquid with a coagulation liquid to form a mixed liquid, and forming a coagulated material containing the polymer compound and the cellulose nanofibers in the mixed liquid; and removing the solvent from the layer of the coagulated material to obtain the composite in the form of a film; The method of claim 10, comprising:

13. a step of removing the solvent from the dispersion to obtain the composite, A step of discharging the dispersion liquid from a nozzle to form a fibrous discharged product; and a step of removing the solvent from the discharged product to obtain the fibrous composite material The method of claim 10, comprising:

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